This is a updated collection of easy to build projects for radio amateurs and swl's.
Have fun.
73 John

Wednesday, June 29, 2011

Travel loop antenna type 40-10 and 80-10

Haunted  as many  others by radio interference and  noise I started looking for a wideband portable antenna . Soon I became focused on a magnetic loop antenna. The only catch was the method of feeding by a Faraday loop , it made the project hand sensitive …. In the Rothammel Antennabook I found a complete different way of feeding made by capacitors .
This was a big  improvement and made a perfect match possible between 6.5 and 30 MHz.
Both tuning capacitors come from old AM radios and because their  sections are switched  in series , they can be used up to 30 Watts without arcing. They interact so it’s wise to make some markings on the front for fast tuning.
The loop is made of RG-213 coax and rests on a cross made of 6 mm. fibreglass rods( kite shop )
Inside the tuner is a shortcut between the centre and the braid of the coax loop to form a solid ring .  By simply adding a second loop with a 5 cm.spacing and a switch to put the loop's in parallel or in series, the antenna becomes a 80-10 m. portable low power loop for travelling. The travelloop was born HI. It has been my travel companion for many years with many qso’s even far over the Atlantic.
Tuning capacitors : http://www.rfparts.com/old_site/caps_antennaload.html

6.5-30 MHz  TRAVEL LOOP

 6.5- 30MHz tuner
3.5- 30 MHz VERSION WITH BANDSWITCH

THE SWITCH SHOWN FROM BEHIND

CAUTION !
Magnetic loop antennas can produce a high voltage that may be harmfull to your health.
Tune your antenna at low power and take a safe distance while operating .
Disclaimer:I'm not responsable for any damage due to reproduction of my projects.

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